Fernando Cordeiro, Piotr Robouch, Ioannis Fiamegkos, M.-F. Tumba-Tshilumba, Aneta Cizek-Stroh and Beatriz de la Calle
EURL-HM-21
Proficiency Test Report
Determination of total As, Cd, Hg, extractable Pb and inorganic As in kaolinitic clay
November 2015
JRC98774
This publication is a Technical report by the Joint Research Centre, the European Commission’s in-house science
service. It aims to provide evidence-based scientific support to the European policy-making process. The scientific
output expressed does not imply a policy position of the European Commission. Neither the European
Commission nor any person acting on behalf of the Commission is responsible for the use which might be made
of this publication.
JRC Science Hub
https://ec.europa.eu/jrc
JRC98774
© European Union, 2015
Reproduction is authorised provided the source is acknowledged.
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How to cite:
Fernando Cordeiro, Piotr Robouch, Ioannis Fiamegkos, M.-F. Tumba-Tshilumba, Aneta Cizek-Stroh and
Beatriz de la Calle; Determination of total As, Cd, Hg, extractable Pb and iAs in kaolinitic clay. JRC98774
1
Determination of total As, Cd, Hg, extractable Pb and inorganic As in kaolinitic clay
Table of contents
Executive summary ............................................................................................... 3
Acknowledgements ................................................................................................ 4
1. Introduction ...................................................................................................... 5
2. Scope and aim .................................................................................................. 5
3. Set up of the exercise ........................................................................................ 6
3.1 Time frame .................................................................................................. 6
3.2 Confidentiality .............................................................................................. 6
3.3 Distribution .................................................................................................. 6
3.4 Instructions to participants ............................................................................. 6
4. Test item .......................................................................................................... 7
4.1 Preparation .................................................................................................. 7
4.2 Homogeneity and stability .............................................................................. 7
5. Assigned values and their uncertainties ................................................................ 7
5.1 Assigned value, Xref ....................................................................................... 7
5.2 Associated uncertainty, uref ............................................................................ 8
5.3 Standard deviation of the proficiency assessment, σ ........................................ 10
5.4 Scores and evaluation criteria ....................................................................... 10
6. Evaluation of results ........................................................................................ 11
6.1 Total Arsenic .............................................................................................. 12
6.2 Inorganic Arsenic ........................................................................................ 13
6.3 Total Cadmium ........................................................................................... 14
6.4 Total Mercury ............................................................................................. 14
6.5 Extractable Lead ......................................................................................... 14
6.6 Compliance ................................................................................................ 15
6.7 Additional observations ................................................................................ 15
7. Conclusion ...................................................................................................... 16
8. References ..................................................................................................... 17
9. Abbreviations .................................................................................................. 19
Annex 1: Invitation letter to NRLs ......................................................................... 20
Annex 2: JRC web announcement ......................................................................... 21
Annex 3: Sample accompanying letter ................................................................... 22
Annex 4: Confirmation of receipt form ................................................................... 23
Annex 5: Questionnaire ....................................................................................... 24
Annex 6: Sample preparation ............................................................................... 27
Annex 7: Homogeneity studies ............................................................................. 29
Annex 8: Results for total arsenic (As) ................................................................... 30
Annex 9: Results for inorganic arsenic (iAs) ............................................................ 32
Annex 10: Results for total cadmium (Cd) .............................................................. 34
Annex 11: Results for total mercury (Hg) ............................................................... 36
Annex 12: Results for extractable lead (ex-Pb) ....................................................... 38
Annex 13: Experimental details and scoring (z-scores) ............................................ 40
Annex 14: Compliance assessment ........................................................................ 48
3
Executive summary
The European Union Reference Laboratory for Heavy Metals in Feed and Food (EURL-HM)
organised a proficiency test (EURL-HM-21) for the determination of total arsenic (As),
cadmium (Cd), mercury (Hg), extractable lead (ex-Pb) and inorganic arsenic (iAs) in
kaolinitic clay in support to Directive 2002/32/EC on undesirable substances in animal
feed.
The present proficiency test (PT) was opened to National Reference Laboratories (NRLs)
and official control laboratories (OCLs). Forty six participants from 29 countries
registered to the exercise. Four participants did not report results.
The material used as test item was a kaolinitic clay feed additive which, after appropriate
processing, was bottled, labelled and dispatched to the participants during the first half
of May 2015. Four laboratories with demonstrated measurement capabilities in the field
provided results to establish the assigned values. The standard uncertainties associated
to the assigned values were calculated according to ISO Guide 35.
Laboratory results were rated using z- and ζ-scores in accordance with ISO 13528. The
relative standard deviation for proficiency assessment was set to 20 % of the assigned
value for total As, and to 25 % for ex-Pb and total Hg. No scoring was provided for the
total Cd and inorganic As.
Most of the laboratories performed satisfactorily (with |z| 2) for the determination of
Hg (94 %), As (82 %) and ex-Pb (71 %, after rejection of the laboratories reporting
total lead mass fraction instead of extractable lead), and reported realistic measurement
uncertainties.
4
Acknowledgements
The authors wish to thank colleagues from the Institute for Reference Materials and
Measurements (IRMM) for their valuable contributions they made during the preparation
and testing of the PT material.
The laboratories listed below are kindly acknowledged for their participation in this
exercise.
Organisation Country
AGES GmbH AUSTRIA
CODA-CERVA BELGIUM
Central Laboratory for Chemical Testing and Control BULGARIA
Croatian Veterinary Institute CROATIA
Department of Agriculture CYPRUS
State Veterinary Institute Olomouc CZECH REPUBLIC
CISTA CZECH REPUBLIC
Veterinary and Food Administration DENMARK
Agricultural Research Centre ESTONIA
Finnish Food Safety Authority Evira FINLAND
Laboratoire SCL de Bordeaux FRANCE
Federal Office for Consumer Protection and Food Safety (BVL) GERMANY
Regional Center of Plant Protection and Quality Control of Magnissia GREECE
General Chemical State Laboratory GREECE
National Food Chain Office Food and Feed Safety Directorate HUNGARY
National Food Chain Safety Office HUNGARY
Health Service Executive IRELAND
Public Analyt's Laboratory Dublin IRELAND
The State Laboratory IRELAND
Istituto Zooprofilattico Sperimentale del Piemonte, Liguria e Valle D'Aosta ITALY
Institute of Food Safety, Animal Health and Environment LATVIA
National Food and Veterinary Risk Assessment Institute LITHUANIA
Environmental Health Directorate MALTA
RIKILT NETHERLANDS
NIFES NORWAY
National Veterinary Research Institute in Pulawy POLAND
Instituto Nacional de Investigação Agrária e Veterinária, I.P PORTUGAL
Hygiene and Veterinary Public Health Institute ROMANIA
Sanitary Veterinary and Food Safety Laboratory Bucharest ROMANIA
Veterinary and food institute in Košice SLOVAKIA
National Laboratory for Health, Environment and Food - Maribor SLOVENIA
National Veterinary Institute SLOVENIA
Jozef Stefan Institute SLOVENIA
MAGRAMA SPAIN
National Veterinary Institute SWEDEN
Fera UNITED KINGDOM
Glasgow Scientific Services UNITED KINGDOM
City of Edinburgh Council UNITED KINGDOM
Staffordshire County Council UNITED KINGDOM
Kent County Council UNITED KINGDOM
5
1. Introduction
The European Union Reference Laboratory for Heavy Metals in Feed and Food (EURL-HM)
organised the proficiency test (PT) EURL-HM-21 to assess the performance of National
Reference Laboratories (NRLs) and official control laboratories (OCLs) in the
determination of total arsenic (As), cadmium (Cd), mercury (Hg), extractable lead
(ex-Pb) and inorganic arsenic (iAs) mass fractions in kaolinitic clay. This PT was
organised as agreed with the Directorate General Health and Food Safety (DG SANTE) in
the annual work program of the EURL-HM.
Kaolinitic clay (KC) is an aluminium silicate mineral, displaying the layered structure of
phillosilicates (parallel sheets of silicates). Among various applications, KC is a
“technological feed additive” used as a “binder” or “anti-caking agent” originally
authorised by Commission Directive 85/429/EEC [1], as listed in the “European Union
Register of Feed Additives” [2].
According to Commission Regulation (EU) No 1275/2013 [3] “[…] Recently, a significant
difference has been identified by the European Union Reference Laboratory for heavy
metals in feed and food (EURL–HM) between the analytical results obtained by the
application of different extraction methods currently used for the determination of lead in
kaolinitic clay and feed containing kaolinitic clay [4]). […] The maximum levels of heavy
metals in feed relate ‘to an analytical determination of lead, whereby extraction is
performed in nitric acid (5 % w/w) for 30 minutes at boiling temperature’. It is therefore
appropriate to provide for the use of that method of extraction for the determination of
lead in kaolinitic clay […]”, as prescribed in the European Standard EN 15510:2007 [5].
This Regulation adds that equivalent extraction procedures may be used provided that
demonstration of equal efficiency is sound.
Furthermore, Directive 2002/32/EC of the European Parliament and of the Council [6]
set maximum levels (MLs) for undesirable substances (such as As, Cd, Hg and Pb) in
animal feed. Regarding iAs, this Directive states that the competent authorities may
request the additional determination of iAs when total As levels higher than 2 mg kg-1
are found; this applies specifically to feedingstuffs for fish.
This report evaluates and summarises the performance of NRLs and OCLs in the
determination of total arsenic, cadmium and mercury, extractable lead and inorganic
arsenic in kaolinitic clay determined in the frame of the PT exercise. Additionally, it
evaluates the ability of laboratories in assessing the compliance of this test item against
the maximum levels set in legislation.
2. Scope and aim
As stated in Regulation (EC) 882/2004 [7] one of the core duties of the EURLs is to
organise interlaboratory comparisons for the benefit of the NRLs.
The present PT aims to assess the performance of NRLs and OCLs in the determination
of total As, Cd, Hg, iAs and extractable Pb mass fractions in kaolinitic clay. In addition,
participants were requested to evaluate the conformity of the analysed feed additive
according to the maximum levels (MLs) set in legislation.
The assessment of measurement results follows the administrative and logistic
procedures of the EC-JRC-IRMM for the organisation of PTs, which is accredited
according to ISO/IEC 17043:2010 [8].
The name of this proficiency test round is EURL-HM-21.
6
3. Set up of the exercise
3.1 Time frame
The organisation of the EURL-HM-21 exercise was agreed upon by the NRL network at
the 8th EURL-HM Workshop held in Brussels on September 24, 2013. Invitation letters
were sent to the NRLs on February 26, 2015 (Annex 1) and a web announcement
(Annex 2) for the exercise was made on the same day on the JRC webpage [9]. The
registration deadline was set to April 10, 2015. The reporting deadline was set to July
24, 2015. Dispatch was followed by the PT coordinator using the messenger's parcel
tracking system on the internet.
3.2 Confidentiality
According to the IRMM procedure for the organisation of PTs the confidentiality of
participants is guaranteed. However, the following confidentiality statement was made to
NRLs: "In case you plan to pay for the participation of official control laboratories
belonging to your national network, please inform them that their identity will be
disclosed to you" (Annex 1).
3.3 Distribution
The test item was dispatched to participants on June 8, 2015. Each participant received:
• One glass bottle containing approximately 15 g of test item;
• A "Sample accompanying letter" (Annex 3); and
• A "Confirmation of receipt form" to be sent back to IRMM after receipt of the test
item (Annex 4).
3.4 Instructions to participants
Detailed instructions were given to participants in the "Sample accompanying letter"
mentioned above. Measurands were defined as "Total As, Cd, Hg, ex-Pb and iAs mass
fractions in kaolinitic clay".
Participants were asked to perform two or three independent measurements, to correct
their measurements for recovery and to report their calculated mean (xlab), the
associated expanded measurement uncertainty (Ulab) together with the corresponding
coverage factor and the technique used. Unlike other PTs where results are reports
related to dry mass, participants were expected to comply with the legal requirements
set by the feed legislation and report results referring to 12 % moisture content. When
participants reported results referring to dry mass these results were systematically
corrected to 12 % moisture content to allow a consistent comparison.
Participants received an individual code to access the on-line reporting interface, to
report their measurement results and to complete the related questionnaire. A dedicated
questionnaire was used to gather additional information related to measurements and
laboratories (Annex 5).
Participants were informed that the procedure used for the analysis should resemble as
closely as possible the one they use in their routine analysis.
The laboratory codes were given randomly and communicated to the participants by
e-mail.
7
4. Test item
4.1 Preparation
The test item used was a commercially available feed additive (kaolinitic clay) kindly
provided by AGS Mineraux (France) and Goonvean (United Kingdom). Ca. 7 kg of
kaolinitic clay were sent to the IRMM. Once received, the material was stored at + 4 °C
until processing. The material was homogenised and portions of 15 g were filled into
125 ml acid-washed amber glass bottles. The bottles were manually filled using acid
washed plastic spoons under an air extraction point. The bottles were closed with acid
washed inserts and screw caps.
Each vial was identified/labelled with a unique number and with the name of the PT
round, following the IRMM procedures.
4.2 Homogeneity and stability
Measurements for the homogeneity and stability studies were performed by Centro de
Salud Pública de Alicante (CSPA, Alicante, Spain). Inductively coupled plasma mass
spectrometry (ICP-MS), after microwave digestion (0.20 g of feed additive in a mixture
of 65 % HNO3 /37 % HCl) was used to determine the total As and Cd mass fractions.
Extractable Pb mass fractions was determined applying the sample extraction procedure
described in Annex 6.
An elemental mercury analyser (EMA) was used to quantify the total Hg mass fraction,
using approximately 200 mg of feed additive per analysis.
The statistical treatment of data was performed by the EURL-HM.
Homogeneity was evaluated according to ISO 13528:2005 [10]. The test item proved to
be adequately homogeneous for the total As, Hg and ex-Pb. However the test item was
found to be not adequately homogeneous for total Cd.
The PT organisers considered that the stability of heavy metals in mineral material (such
as kaolinitic clay) is granted and not to be demonstrated. However, the stability study
confirmed that the material was stable and the uncertainty contribution due to stability
was set to zero (ust = 0) for all analytes.
The contribution from homogeneity (ubb) to the standard measurement uncertainty of
the assigned value (uref) was calculated using SoftCRM [11]. The analytical results
reported by the expert laboratory and the statistical evaluation of the homogeneity study
are presented in Table 1 and in Annex 7.
5. Assigned values and their uncertainties
5.1 Assigned value, Xref
The assigned values for the five measurands (total As, Cd, Hg, ex-Pb and iAs in kaolinitic
clay) were determined by four laboratories, selected on the basis of their demonstrated
measurement capabilities (later referred as expert laboratories):
• ALS Scandinavia AB (Luleå, Sweden);
• SCK-CEN - Studiecentrum voor Kernenergie (Mol, Belgium);
• UBA - Environmental Agency Austria (Vienna, Austria);
• CSPA - Centro de Salud Pública de Alicante (Alicante, Spain)
8
Expert laboratories were asked to use the method of analysis of their choice and no
further requirements were imposed regarding methodology. They were requested to
analyse three independent replicates per bottle (two bottles were distributed for each
expert laboratory), on two different days (one bottle per day).
Expert laboratories were also required to report their results together with the
associated expanded measurement uncertainty and with a clear and detailed description
on how their measurement uncertainty was evaluated. Expert laboratories were not
requested to report values for all measurands.
• ALS Scandinavia used inductively coupled plasma sector field mass spectrometry
(ICP-SFMS) after digestion with HNO3, HCl and HF in sealed Teflon containers in
microwave oven, for the analysis of the total As, Cd and Hg. Ion chromatography
with post column hydride generation and detection by ICP coupled with mass
spectrometry detector (IC-ICP-MS) was used for the determination of iAs. ALS
followed the protocol provided by IRMM for the quantification of ex-Pb (Annex 7).
SCK-CEN applied the k0-standardized neutron activation analysis (k0-NAA) for the
determination of total As, Cd and Hg. Three test samples of about 400 mg were
taken from each bottle and transferred in standard high-density polyethylene
vials and weighed. Samples were irradiated for seven hours in the BR1 reactor
under a thermal flux of 3 1011 n s-1 cm2 together with four IRMM-530
(Al-0.1 % Au alloy) neutron flux monitors, and several reference materials for
validation (SMELS II; SMELS III; BCR 176 - fly ash; and BCR 278 - mussel
tissue). Two spectra per sample were then collected (after 3 and 14 days) on a
k0-calibrated HPGe detector. No additional sample treatment was applied.
• Umweltbundesamt GmbH (UBA) used graphite furnace atomic absorption
spectrometry (GF-AAS) for the analysis of total As and Cd, while cold-vapour
atomic absorption spectrometry (CV-AAS) was used to determine the total Hg.
Microwave-assisted high-pressure digestion was used with HNO3, HCl and HF for
digestion. Complexation with H3BO4 according to ÖNORM EN 13656 was used.
• CSPA used ICP-MS after digestion with an acid mixture of 65 % HNO3 /37 % HCl,
for the determination of the total As and Cd. EMA was used for the total Hg which
consists of a single purpose atomic absorption spectrophotometer for Hg
determination. For the extractable Pb determination the extraction protocol
provided by IRMM was followed, after which, ICP-MS was used as technique.
For this PT, the mean of the retained means reported by the expert laboratories were
used to derive the assigned values (Xref) according to ISO Guide 35:2006 [12]
(Figure 1).
No reference values were assigned for Cd and iAs, as discussed later.
5.2 Associated uncertainty, uref
The associated standard measurement uncertainties (uref) of the assigned values were
calculated following the law of propagation of uncertainty, combining the standard
measurement uncertainty of the characterization (uchar) with the standard uncertainty
contribution from homogeneity (ubb) in compliance with ISO Guide 35 [12]:
22
bbcharref uuu Eq. 1
For the total As, Hg and ex-Pb, expert laboratories reported values with overlapping
expanded measurement uncertainties (Table 1, Figure 1), hence uchar was calculated
according to ISO 13528:2005 [10]:
9
p
ichar up
u1
225.1
Eq. 2
where: p is the number of expert laboratories used to assign the reference value; and
ui is the standard measurement uncertainty reported by the expert
laboratories.
Table 1 presents the average measurement values reported by the expert laboratories
and their associated expanded measurement uncertainties; the assigned values (Xref, uref
and Uref (k=2)); the standard measurement uncertainty contributions (uchar and ubb); and
the standard deviation for PT assessment (σ). All values were corrected to 12 %
moisture content in order to comply with the feed legislation [6].
Figure 1: Assigned values for EURL-HM-21. Circles represent the reported values by the retained
expert laboratories (± 2ui); the solid line represents the assigned value (Xref) while the dashed lines represent the expanded assigned uncertainty interval (Xref ± Uref).
Table 1 – Results reported by expert laboratories and their associated expanded measurement
uncertainties; the assigned values (Xref, uref and Uref (k=2)); the standard measurement uncertainties (uchar and ubb); and the standard deviation for PT assessment (σ). All values are expressed in mg kg-1. All values refer to 12% moisture.
As Hg ex-Pb Cd iAs
Expert 1 5.12 ± 0.50a 0.040 ± 0.005 3.27 ± 0.43 0.106 ± 0.015
Expert 2 7.57 ± 0.76 0.054 ± 0.008 3.05 ± 0.31 0.136 ± 0.013 0.91 ± 0.091
Expert 3 7.81 ± 0.78 0.047 ± 0.004 0.041 ± 0.007
Expert 4 8.42 ± 0.17 < 0.5 < 0.9
Xref 7.93 0.047 3.15
uchar 0.23 0.002 0.17
ubb 0.34 0.001 0.15
uref 0.41 0.002 0.22
Uref 0.82 0.004 0.45
σ 1.59 0.012 0.79 no scoring no scoring
σ (%) 20% 25% 25%
0.3σ 0.48 0.003 0.24
uref < 0.3 σ ? yes yes yes
a Rejected result (see Section 6.1)
6.4
7.2
8.0
8.8
9.6
mass f
raction (
mg k
g-1)
expert laboratories
Total Arsenic
0.02
0.03
0.04
0.05
0.06
0.07
0.08
mass fra
ction (
mg k
g-1)
expert laboratories
Total Mercury
2.0
2.5
3.0
3.5
4.0
4.5
mass fra
ction (
mg k
g-1)
expert laboratories
extractable Lead
10
5.3 Standard deviation for proficiency assessment, σ
The relative standard deviation for proficiency assessment (σ, in %) was set considering
the performance of participants in previous PT rounds with similar measurands [9] and
taking into account the complexity of the test item investigated. Therefore, σ was set to
20 % of the assigned value for total As, and to 25 % for ex-Pb and Hg (Table 1).
5.4 Scores and evaluation criteria
Individual laboratory performance was expressed in terms of z- and ζ-scores in
accordance with ISO 13528:2005 [10]:
z = σ
refXx lab Eq. 3
22
labref
lab
uu
refXx
Eq. 4
where: xlab is the measurement result reported by a participant;
ulab is the standard measurement uncertainty reported by a participant;
Xref is the assigned value;
uref is the standard measurement uncertainty of the assigned value;
σ is the standard deviation for proficiency assessment.
The interpretation of the z- and ζ-scores is done according to ISO 17043:2010 [8]:
|score| ≤ 2 satisfactory performance (green in Annexes 8 - 13);
2 < |score| < 3 questionable performance (yellow in Annexes 8 - 13);
|score| ≥ 3 unsatisfactory performance (red in Annexes 8 - 13).
The z-score compares the participant's deviation from the assigned value with the
standard deviation for proficiency assessment (σ) used as common quality criterion.
The ζ-score states whether the laboratory's result agrees with the assigned value within
the respective uncertainty. The denominator is the combined uncertainty of the assigned
value (uref) and the measurement uncertainty as stated by the laboratory (ulab). The
ζ-score includes all parts of a measurement result, namely the expected value (assigned
value), its measurement uncertainty in the unit of the result as well as the uncertainty of
the reported values. An unsatisfactory ζ-score can either be caused by the presence of a
significant bias (inaccurate measurement) or by a not realistic estimation of its
measurement uncertainty (seriously under-estimated), or both.
The standard measurement uncertainty of the laboratory (ulab) was obtained by dividing
the reported expanded measurement uncertainty by the reported coverage factor, k.
When no uncertainty was reported, it was set to zero (ulab = 0).
Uncertainty estimation is not trivial, therefore an additional assessment was provided to
each laboratory reporting measurement uncertainty, indicating how reasonable their
measurement uncertainty evaluation was.
The standard measurement uncertainty from the laboratory (ulab) is most likely to fall in
a range between a minimum uncertainty (umin), and a maximum allowed (umax) –
case "a": umin ≤ ulab ≤ umax. umin is set to the standard measurement uncertainty of the
assigned value (umin = uref). It is unlikely that a laboratory carrying out the analysis on a
routine basis would measure the measurand with a smaller measurement uncertainty
than the expert laboratories chosen to establish the assigned value. umax is set to the
standard deviation accepted for the PT assessment (umax = σ). Consequently, Case "a"
becomes: uref ≤ ulab ≤ σ.
11
If ulab is smaller than umin (case "b": ulab < uref) the laboratory may have underestimated
its measurement uncertainty. Such a statement has to be taken with care as each
laboratory reported only its measurement uncertainty, whereas the uncertainty
associated with the assigned value also includes the contribution for homogeneity of the
test item. If that is large, measurement uncertainties smaller than umin are possible and
plausible.
If ulab is larger than umax (case "c": ulab > σ) the laboratory may have overestimated its
measurement uncertainty. An evaluation of this statement can be made when looking at
the difference between the reported value and the assigned value: if the difference is
smaller than Uref then overestimation is likely. If the difference is larger but xlab agrees
with Xref within their respective expanded measurement uncertainties, then the
measurement uncertainty is properly assessed resulting in a satisfactory performance
expressed as a ζ-score, though the corresponding performance, expressed as a z-score,
may be questionable or unsatisfactory.
It should be pointed out that umax is a normative criterion when set by legislation.
More detailed information about measurement uncertainty evaluation can be found in
some international standard and other guidance documents [13-17].
6. Evaluation of results
Kaolinitic clay is a layer structured mineral (inorganic) material that can trap/bind ions,
metals and mycotoxins. The total extraction of an element (i.e. As, Cd, Hg, Pb) from
such matrix would require the use of strong acid mixtures to break the bonds
trapping/fixing cations to the clay. Several strong acid mixtures (including HNO3, HCl
and/or H2SO4) were used successfully in this exercise. The supplementary addition of HF
was proven to be effective by the expert laboratories and participating laboratories.
For the determination of extractable lead the use of 5 % HNO3 (weaker acid) is
prescribed by Commission Regulation (EU) No 1275/2013 [3].
The sample preparation protocol, described in EN 16278 [18] for the determination of
inorganic arsenic prescribes the use of HNO3 and H2O2. The effectiveness of this acid
mixture is discussed below.
Several challenges are therefore identified for this PT:
- the determination of total arsenic, cadmium and mercury;
- the determination of inorganic arsenic;
- the determination of extractable lead; and
- the compliance assessment of the test item used as feed additive as such, or
included in feedingstuffs, according to the relevant EU legislation.
Annexes 8 to 12 present for each measurand the table of results as reported by the
participants and systematically corrected to 12 % moisture content to allow a consistent
comparison in compliance with European legislation [6]. NRLs and OCLs are denoted as
Nxx and Lxx, respectively. The corresponding Kernel density plots are also included,
obtained using the software available from the Statistical Subcommittee of the Analytical
Methods Committee of the UK Royal Society of Chemistry [19]. All the experimental
details collected via the questionnaire are summarised in Annex 13.
From the 46 laboratories having registered to this PT 4 did not report results, of which
one NRL. The NRL from Luxemburg did not register to this PT. Some participants
reported truncated ("less than") values: 5 for total Cd, 6 for total Hg, and one for iAs. All
of them (except one) are realistic, because these values where above the lower limit of
the assigned range (Xref - Uref).
Figure 2 presents the z- and -score distribution for NRLs and OCLs.
12
Figure 2: Overview of the z and -scores obtained by NRLs and OCLs for the
different measurands. The data shown for ex-Pb (*) are obtained excluding the "outlying" values (see Section 6.5). Satisfactory, questionable and unsatisfactory performances - expressed as z- and -scores - are indicated in green, yellow and red, respectively.
The evaluation of the results reported by the participants is thoroughly discussed
hereafter.
6.1 Total arsenic
The homogeneity of the test material was proven to be adequate for total As (Annex 6).
One of the expert laboratories applied k0-NAA, a method of choice for the determination
of arsenic in soil type matrices. This result was further confirmed by two other expert
laboratories having applied ICP-MS, after closed microwave digestion with a strong acid
mixture including HF. However, "Expert 1" did not use HF in the acid mixture for
digestion and reported a significantly lower total arsenic value. This may be attributed to
an incomplete extraction of total arsenic, and the PT organiser did not include this result
in the calculation of the assigned value. The following assigned range was derived: 7.93
± 0.82 (k=2) mg kg-1; where the standard uncertainty of the assigned value (0.41 mg
kg-1) was smaller than 0.3 (0.48 mg kg-1, Table 1).
A total of 38 results were reported and the Kernel density plot indicates the presence of
two partially overlaying normal distributions (Annex 8). The majority of the laboratories
and "Expert 1" belong to the first mode (ca. 5.6 mg kg-1), while laboratory N35 (using
k0-NAA) and laboratories N12, N31 L24 and N27 (having used strong acid mixtures
including HF) confirm the second mode at 7.8 mg kg-1, and therefore the assigned value.
2726
1818
5 0
4
4
02
83
0%
20%
40%
60%
80%
100%
As Hg ex-Pb ex-Pb (*)
z-scores (NRLs)
4
3
2
2
2
0
0
0
0 0
4
1
0%
20%
40%
60%
80%
100%
As Hg ex-Pb ex-Pb (*)
z-scores (OCLs)
11
1715
15
6
6
1
1
15
5
149
0%
20%
40%
60%
80%
100%
As Hg ex-Pb ex-Pb (*)
ζ-scores (NRLs)
1
2
2
2
1
1
0
04
0
4
1
0%
20%
40%
60%
80%
100%
As Hg ex-Pb ex-Pb (*)
ζ-scores (OCLs)
13
Most of the participants used inductively coupled plasma mass spectrometry (ICP-MS),
hydride generation atomic absorption spectrometry (HG-AAS) or graphite furnace AAS
(GF-AAS). No significant trend could be observed related with the analytical technique.
Due to the challenging extraction of analytes from the clay matrix investigated, the PT
organisers set to 20 % of the assigned value, a value significantly higher than the one
predicted by the Horwitz equation. The resulting acceptable range (Xref ± 2σ)
encompasses the whole observed bimodal distribution. Therefore 82 % of the
laboratories (31/38) obtained a satisfactory performance, expressed as z-score (|z| ≤ 2,
Figure 2). The remaining results were under-estimated (-2.69 < z < -2.03), probably
due to the use of milder acid mixtures for digestion (HNO3 or HNO3/H2O2 at low
concentrations, below 10 % v/v).
However, despite the fact that the majority of laboratories reported realistic
uncertainties (of the order of 10 to 15 %) a large fraction of the population got an
unsatisfactory performance expressed as -score (|| 3, Figure 2). This is attributed to
the difference between the two modes of ca. 33 %, which is significantly larger than the
standard measurements uncertainty reported. Taking into consideration the difficult
matrix analysed, laboratories are advised to revise their sample treatment (digestion,
acid mixture) and correct for their bias, instead of reviewing their measurement
uncertainty evaluation.
6.2 Inorganic arsenic
While the homogeneous distribution of iAs in the test item was assumed to be similar to
the one of total As, only the "Expert 2" laboratory reported a value for iAs (0.91 ± 0.09
mg kg-1) applying ICP-MS after microwave digestion with H3PO4 (Table 1). This value is
significantly lower than the value reported by "Expert 2" for total As (7.57 ± 0.76
mg kg-1), which seems unrealistic for a mineral/clay matrix, where iAs is expected to be
the major arsenic constituent. Hence, no assigned value was attributed by the PT
organiser for this measurand and no scoring of results was performed.
Thirteen laboratories reported highly scattered results for iAs, ranging from 0.13 to 6.3
mg kg-1 (Annex 9) – well below the value assigned for total As. Figure 2 presents the 12
results reported for As and iAs. Three of the laboratories (N26, N04 and N12) reported
satisfactory total arsenic results (|| 1.6), close to the vertical line. Three other
laboratories (L44, L45 and N20) used the HCl/HNO3 (strong) acid mixture for digestion
and obtained similar mass fractions for both analytes, (close to the diagonal line). The
rest of the participants under-estimated both measurand values. As a conclusion, the
classical acid mixture used for the determination of iAs may not be suitable to extract
the “total” inorganic arsenic present in kaolinitic clay.
Figure 3: The results of 12 laboratories having reported results for total and inorganic arsenic.
14
6.3 Total cadmium
The expert laboratories reported highly scattered values for Cd in kaolinitic clay ranging
from 0.04 to 0.14 mg kg-1 (Table 1) and the homogeneity results could not demonstrate
the fitness-for-purpose of the material (ubb > 0.3 ; Annex 7). Therefore, no assigned
value could be established and no scoring of the results was performed.
Nevertheless, a total of 35 results were reported (Annex 10). Most of them were in the
same range observed by the expert laboratories. Only three laboratories (N30, L36 and
L44) reported significantly higher values (ca. 0.4 mg kg-1). Algorithm A of ISO 13528
was used to compute an informative “consensus value” of 0.065 mg kg-1 from all the
results reported by the participants. Although the PT organiser does not guarantee the
representativeness of this value for the total cadmium content in the kaolinitic clay test
item, participants may consider comparing their performance by mean of the D% score,
as defined in ISO 13528 [10].
6.4 Total mercury
The homogeneity of the test material was proven to be adequate for total Hg (Annex 7).
Due to the challenging matrix investigated and the low mercury content the PT
organisers set to 25 % of the assigned value. The results provided by the three expert
laboratories were in agreement (Table 1).
All the participants using ICP-MS (10 out of 10) and elemental mercury analyser (EMA,
11 out of 11) reported satisfactory results similarly to the 8 participants (out of 10)
using CV-AAS. No significant trend could be observed related with the analytical
technique. All laboratories used strong acid mixtures with closed microwave digestion
systems. The four laboratories (N31, N35, N12 and N27) having added HF confirmed the
assigned value (Annex 11).
94 % of the laboratories (29/31) obtained satisfactory performance expressed as z-score
(|z| ≤ 2, Figure 2), while 61 % of the laboratories (19/31) obtained satisfactory
performance expressed as -score.
6.5 Extractable lead
The homogeneity of the test material was proven to be adequate for ex-Pb (Annex 7).
Two expert laboratories provided results that were in agreement from which the
assigned range was derived: 3.15 ± 0.44 (k=2) mg kg-1; where the uncertainty of the
assigned value was smaller than 0.3 (0.24 mg kg-1, Table 1).
Expert laboratories and all participants were requested to quantify “extractable lead”
applying the recommendations set in Commission Regulation (EU) No 1275/2013. Eight
participants (out of 36) erroneously applied closed microwave (CMW) digestion with
strong acid mixtures (instead of the prescribed 5 % HNO3) and reported (outlying)
values above 40 mg kg-1 (Annex 12). Three of them (N17, L42 and L43) acknowledged
having analysed "total lead" instead of the requested "extractable lead". Most of the
participants followed the standard operating procedure described in EN 15510 (Annex 7)
[5], varying the ratio "sample intake / volume of HNO3 (5 %)". The following
instrumental techniques were mainly used: ICP-MS and electro thermal AAS (ET-AAS).
No significant trend could be observed related with the analytical technique. None of the
participants used the ICP-AES technique recommended in EN 15510 [5].
After removal of the "outlying" data, 71 % (20/28) obtained a satisfactory performance,
expressed as z-score (|z| ≤ 2, Figure 2). Similarly, 61 % (17/28) obtained a satisfactory
performance expressed as -score (|| ≤ 2, Figure 2). Five laboratories submitted results
ranging from 4.4 to 4.9 mg kg-1 (48 % above the assigned value) and reported likely
under-estimated standard measurement uncertainties (below 10 %).
15
Figure 2 also presents the z- and -score of the complete set of results reported for
extractable lead (including the "outlying" values mentioned above) for which the
number of unsatisfactory results (|z| and || > 3) is significantly increased.
6.6 Compliance
Kaolinitic clay is commonly classified as “technological feed additive” and used as
“binder” or “anti-caking agent” [1, 2].
Similarly to other bentonite/montmorillonite clays, this feed additive (FA) is intended to
be included in feedingstuffs (FS) at concentration levels ranging from 1 to 25 g kg-1 [20].
The assigned values for total As, Hg and ex-Pb are compared as such (Xref in FA) or
converted into an "hypothetical" content in feed (25 g of kaolinitic clay per kilogram
feed, corresponding to a dilution factor of 40) to the maximum levels for undesirable
substances (i.e. As, Cd, Hg and Pb) set by Directive 2002/32/EC [6] (Table 2). Since all
levels are below the MLs, the test item is considered by the PT organiser as compliant.
Table 2 - Assigned values (Xref) and maximum limits (ML) in Feed Additive (FA) or
Feedingstuffs (FS). All values are expressed in mg kg-1.
Analyte Xref in FA Xref in FSa ML [6] in which matrix?
As 7.93 0.20 2 12
in feed material in mineral feedingstuffs
Cd -- -- 2 in binder or anticaking FA
Hg 0.047 0.001 0.1 in feed material
ex-Pb 3.15 -- 30 in binder or anticaking FA a
Applying a dilution factor of 40 to take into account the condition of use of this feed
additive in feedingstuffs.
Annex 14 summarises the compliance statements provided by the participants. 69 % of
the 39 laboratories stated correctly that the material is compliant (cf. green cells in
Annex 14). 13 % of them concluded that the material was not compliant, based on their
outlying results reported while analysing lead - instead of extractable lead (yellow cells
in Annex 14). Finally, six laboratories interpreted erroneously Directive 2002/32/EC [6]
comparing their results for As in kaolinitic clay (feed additive) to the ML for As in feed
material and concluded incorrectly that the material was not compliant.
6.7 Additional observations
Most of the participants (85 %) are NRLs, accredited according to ISO/IEC 17025 for the
analysis of As, Cd, Hg and Pb in feed. However, they do not monitor regularly inorganic
arsenic in mineral matrices; hence, this type of analysis is usually not included in their
accreditation scope.
Participants claiming to analyse more than 250 samples/year reported satisfactory
results for As and/or Hg.
Several CEN standard methods (i.e. EN 15510 [5]; EN 15550 [21], EN 15621 [22] and
EN 16206 [23]) are available for the elemental analysis in feed, applying GF-AAS or ICP-
AES. However, none of these standards are designed for the accurate quantification of
total As, Hg and Pb in clay matrices. Laboratories used the sample preparation protocol
described in the standard but did not use the instrumental approach prescribed. The only
standard available for the determination of iAs in feedingstuffs (EN 16278 [18]) may not
be adequate for the analysis of clay matrices (i.e. kaolinitic clay), since it uses "diluted
hydrochloric acid and hydrogen peroxide solution coupled with microwave assisted
heating". None of the participants succeeded to extract properly the "total" inorganic
arsenic present in the clay.
16
Participants evaluated their measurement uncertainty using one or several of the
following approaches: - applying the "Guide to the expression of uncertainty in
measurement, GUM" [13] (9 laboratories); - from their in-house method validation
studies (27 laboratories); - from inter-laboratory comparison results (8 laboratories)
and/or - from precision data (8 laboratories). Two thirds of all laboratories seem to
report realistic uncertainties (case "a", Annex 8-12). However, this did not ensure
systematically satisfactory z-scores. This may be attributed to the significant biases
observed, such as (i) the insufficient extraction of the "total" As from the clay matrix (as
indicated by the 1st mode at 5.6 mg kg-1); or (ii) the over-estimated extractable Pb
levels due to the use of an extraction procedure stronger than the one prescribed [3,5].
7. Conclusion
Considering the overall satisfactory performance of the participating laboratories in
EURL-HM-21, the analytical capability of the participating laboratories for the
determination of total As, Hg and extractable Pb in kaolinitic clay was successfully
demonstrated at the investigated concentration levels.
As a whole, the NRLs presented good uncertainty evaluations. This may be due to (i) the
several PTs organised so far by the EURL-HM and (ii) the various trainings on relevant
topics related to the analyses of heavy metals in feed and food provided by the EURL-HM
during the annual workshops.
No scoring was provided for total Cd and inorganic As. The first showed inadequate
homogeneity, while the latter appeared to be difficult to extract from the clay matrix
when mild acid mixtures (5 % HNO3/H2O2) for digestion are used.
For the accurate determination of extractable lead mass fractions in kaolinitic clays (and
other phyllosilicates) laboratories must follow the experimental protocol prescribed by
Commission Regulation (EU) No. 1275/2013. The use of higher concentration of acid
mixtures for sample digestion may lead to significantly over-estimated results.
In order to assess the compliance of this particular clay, laboratories must properly
interpret the EU legislation and select the relevant legal maximum levels in feed
additives (e.g. Cd, ex-Pb) and in various feedingstuffs (e.g. As, Hg).
Taking into consideration the difficult matrix analysed, laboratories are advised to revise
their sample treatment (digestion procedure and acid mixtures) rather than reviewing
their measurement uncertainty evaluation.
17
8. References
1. Commission Directive 85/429/EEC of 8 July 1985 amending the annexes to
Council Directive 70/524/EEC concerning additives in feedingstuffs, Official Journal of the European Union, L245 (1985).
2. European Union register of feed additives, available at:
http://ec.europa.eu/food/food/animalnutrition/feedadditives/docs/comm_register feed_additives_1831-03.pdf
3. Commission Regulation (EU) N˚ 1275/2013 amending Annex I to Directive 2002/32/EC. Official Journal of the European Union, L 328 (2013).
4. "Determination of the ratio between the extractable and the total lead contents in
a selection of raw and processed kaolinitic clays", M. B. de la Calle et al., JRC
69122 (2012).
5. EN 15510:2007, "Animal feeding stuffs - Determination of calcium, sodium,
phosphorus, magnesium, potassium, iron, zinc, copper, manganese, cobalt,
molybdenum, arsenic, lead and cadmium by ICP-AES", issued by the European Committee for Standardization.
6. Directive 2002/32/EC on undesirable substances in animal feed. Official Journal of
the European Union, L 140 (2002).
7. Regulation (EC) N˚ 882/2004 of The European Parliament and of The Council of
29 April 2004, on official controls performed to ensure the verification of
compliance with feed and food law, animal health and animal welfare rules. Official Journal of the European Union, L 165 (2004).
8. ISO 17043:2010, "Conformity assessment - General requirements for proficiency
testing", issued by ISO-Geneva (CH), International Organization for Standardization.
9. See IMEP-105, IMEP-108, IMEP-111, IMEP-114 and IMEP-117 https://ec.europa.eu/jrc/en/interlaboratory-comparisons
10. ISO 13528:2005, "Statistical Methods for Use in Proficiency Testing by Inter-
laboratory Comparisons", issued by ISO-Geneva (CH), International Organization
for Standardization.
11. SoftCRM, http://www.eie.gr/iopc/softcrm/index.html, (Accessed at date of publication of this report).
12. ISO Guide 35:2006, "Reference Materials - General and statistical principles for
certification", issued by ISO-Geneva (CH), International Organization for Standardization.
13. ISO/IEC Guide 98:2008, "Uncertainty of measurement - Part 3: Guide to the
expression of uncertainty in measurement" (GUM 1995), issued by the ISO-
Geneva (CH). Available also from the Joint Committee for Guides in Metrology
(JCGM 100:2008) at: http://www.bipm.org/utils/common/documents/jcgm/JCGM_100_2008_E.pdf
14. Eurachem/CITAC, "Quantifying Uncertainty in Analytical Measurement".
http://www.eurachem.org., 3rd Ed. (2012).
15. ISO 21748:2010: "Guidance for the use of repeatability, reproducibility and
trueness estimates in measurement uncertainty estimation", issued by ISO-Geneva (CH), International Organization for Standardization.
16. "Is my uncertainty realistic?", AMC Technical Brief N˚15, issued by the Analytical
Methods Committee (AMC) of the Royal Society of Chemistry, UK (2003).
Available at: http://www.rsc.org/images/realistic-estimate-technical-brief-15_tcm18-214874.pdf
18
17. Eurolab Technical Report 1/2007, "Measurement uncertainty revisited: Alternative
approach to uncertainty evaluation, available at:
http://www.eurolab.org/documents/1-2007.pdf
18. EN 16278:2012, "Animal feeding stuffs. Determination of inorganic arsenic by
hydride generation atomic absorption spectrometry (HG-AAS) after microwave
extraction and separation by solid phase extraction (SPE)", issued by the European Committee for Standardization.
19. EN 16206:2012, "Animal feeding stuffs. Determination of arsenic by hydride
generation atomic absorption spectrometry (HGAAS) after microwave pressure
digestion (digestion with 65 % nitric acid and 30 % hydrogen peroxide), ", issued by the European Committee for Standardization.
20. "Representing data distributions with kernel density estimates", AMC Technical
Brief N˚ 4, issued by the Statistical Subcommittee of the Analytical Methods
Committee (AMC) of the Royal Society of Chemistry, UK, (2006).
21. EURL-FA evaluation reports: FAD-2011-0002, FAD-2010-0018 and FAD-2010-
0233, available from: https://ec.europa.eu/jrc/en/eurl/feed-additives/evaluation-reports
22. EN 15550:2007, "Animal feeding stuffs - Determination of cadmium and lead by
graphite furnace atomic absorption spectrometry (GF-AAS) after pressure
digestion", issued by the European Committee for Standardization.
23. EN 15621:2012, "Animal feeding stuffs - Determination of calcium, sodium,
phosphorus, magnesium, potassium, sulphur, iron, zinc, copper, manganese and
cobalt after pressure digestion by ICP-AES", issued by the European Committee for Standardization.
24. EN 16206:2012, "Animal feeding stuffs - Determination of arsenic by hydride
generation atomic absorption spectrometry (HG-AAS) after microwave pressure
digestion (digestion with 65 % nitric acid and 30 % hydrogen peroxide)", issued by the European Committee for Standardization.
19
9. Abbreviations
AAS Atomic Absorption Spectroscopy
CITAC Cooperation on International Traceability in Analytical Chemistry
CRM Certified Reference Material
CV-AAS Cold Vapour Atomic Absorption Spectrometry
CV-AFS Cold Vapour Atomic Fluorescence Spectrometry
CMW Closed microwave
DA Dry Ashing
EMA Elemental Mercury Analyser (or direct mercury analyser, DMA, Annex 11)
ET-AAS Electro Thermal Atomic Absorption Spectrometry (also called Graphite
Furnace Atomic Absorption Spectroscopy, GF-AAS)
EURL-HM European Union Reference Laboratory for Heavy Metals in Feed and Food
EU European Union
GUM Guide to the expression of Uncertainty in Measurement
HG-AAS Hydride Generation Atomic Absorption Spectroscopy
HPLC-ICP-MS High Performance Liquid Chromatography coupled with ICP-MS
IC-ICP-MS Ion chromatography coupled with ICP-MS
ICP-AES Inductively Coupled Plasma Atomic Emission Spectrometry
ICP-MS Inductively Coupled Plasma Mass Spectrometry
ICP-OES Inductively Coupled Plasma Optical Emission Spectrometry
ICP-ID-MS Inductively Coupled Plasma Isotope Dilution Mass Spectrometry
ICP-SF-MS Inductively Coupled Plasma Sector Field Mass Spectrometry
ILC Interlaboratory Comparison
IMEP International Measurement Evaluation Programme
IRMM Institute for Reference Materials and Measurements
ISO International Organisation for Standardisation
JRC Joint Research Centre
LC-ICP-MS Liquid Chromatography coupled with ICP-MS
k0-NAA k0-standardised Neutron Activation Analysis
NRL National Reference Laboratory
ML Maximum level
OCL Official Control Laboratory
PT Proficiency Testing
Q-ICP-MS Quadrupole Inductively Coupled Plasma Mass Spectroscopy
Z-ET-AAS Zeeman- Electro Thermal Atomic Absorption Spectrometry
20
Annex 1: Invitation letter to NRLs
21
Annex 2: JRC web announcement
https://ec.europa.eu/jrc/en/interlaboratory-comparison/eurl-hm-21?search&form-return
Annex 3: Sample accompanying letter
Annex 4: Confirmation of receipt form
24
Annex 5: Questionnaire
25
26
27
Annex 6: Sample preparation
for the determination of extractable lead in kaolinitic clay
The extractable lead should be analysed following the protocol:
a) Weigh about 2 g of the test sample to the nearest 1 mg into a 250 mL beaker;
b) Add 85 mL of a 5 % (w/w) HNO3 solution(#);
c) Cover the beaker with a watch-glass and boil for 30 min on a hot plate (make
sure that the plate warms up homogeneously all over the surface);
d) Allow to cool. Decant the liquid into a 100 mL volumetric flask, rinsing the beaker
and the watch-glass several times with 5 % (w/w) HNO3;
e) Dilute to the mark with 5 % (w/w) HNO3;
f) After homogenising, filter through a dry folded filter paper into a dry container.
Use the first portion of the filtrate to rinse the glassware and discard that part. If
the determination is not carried out immediately, the container with filtrate shall
be covered;
g) Carry out a blank test at the same time as the extraction, with only the reagents
and follow the same procedure as for the samples.
(#) To prepare 1 kg stock of 5 % (w/w) HNO3 (density ~ 1.0257 kg L-1): mix 77 g of 65
% (w/w) HNO3 with 923 g water. Use a balance of two digits for the weighing.
Note: Method derived from EN 15510:2007 [5] and recommended in the JRC report
[4].
28
29
Annex 7: Homogeneity studies
Normalised values to the mean for each set (X): xi/X (all values in mg kg-1)
As Cd Hg ex-Pb
Sample Nr. R1 R2 R1 R2 R1 R2 R1 R2
2 1.01 1.00 1.067 0.950 0.933 1.044 1.082 1.082
133 1.07 1.04 1.183 1.083 0.978 0.978 1.096 1.099
25 0.97 0.95 0.867 0.867 1.111 0.933 0.984 1.041
144 1.01 1.04 1.092 1.075 1.089 1.022 1.008 0.953
161 0.96 0.97 0.875 0.875 1.022 1.000 1.038 0.973
91 0.96 0.95 0.950 1.017 1.089 1.044 1.011 0.970
113 1.08 1.06 0.992 0.983 1.000 1.067 0.997 0.964
39 0.95 0.95 0.925 0.925 0.933 0.867 0.975 0.970
63 1.03 1.03 1.233 1.175 1.089 1.000 0.874 0.984
77 0.97 0.98 0.967 0.958 0.978 1.022 0.951 0.934
Mean 1.00 1.000 1.000 1.000
σ 1.35 0.010 0.012 0.61
0.3*σ 0.41 0.003 0.003 0.183
Sx 0.272 0.013 0.002 0.198
Sw 0.079 0.005 0.003 0.131
SS (ubb) 0.27 0.013 0.001 0.174
SS ≤0.3*σ? Yes No Yes Yes
where: σ is the standard deviation for the PT assessment (as a % of Xref),
Sx is the standard deviation of the sample averages,
Sw is the within-sample standard deviation,
Ss is the between-sample standard deviation.
30
Annex 8: Results for total arsenic (As)
Assigned values: Xref = 7.93; Uref = 0.82; σ = 1.59
(all values in mg kg-1, referring to 12% moisture content)
a performance: satisfactory, questionable, unsatisfactory, b a: uref ≤ ulab ≤ σ; b: ulab < uref; and c: ulab > σ
DM: dry mass; NC: not corrected for moisture content; 12 %: moisture content of 12 %.
Lab
codeXlab Ulab Xlab12% Ulab12% k ulab12% Technique z-score
aζ-score
aMU
b
N01 12% 4.58 0.92 4.58 0.92 2 0.46 ICP-MS Q -2.11 -5.43 a
N02 NC 6.59 1.27 5.80 1.12 2 0.56 AAS -1.34 -3.08 a
N03 DM 7.24 0.72 6.37 0.63 2 0.32 ICP -0.98 -3.01 b
N04 DM 6.7 2.68 5.90 2.36 2 1.18 ICP-MS -1.28 -1.63 a
N06 DM 8.87 1.6 7.81 1.41 2 0.70 ICP -0.08 -0.16 a
N07 12% 5.2 1.2 5.2 1.2 2 0.6 ICP-MS -1.72 -3.76 a
N08 12% 6.5 1.1 6.5 1.1 2 0.55 ICP-MS -0.90 -2.09 a
N09 DM 6.17 0.62 5.43 0.55 2 0.27 ICP-MS -1.58 -5.07 b
N10 DM 6.39 1.6 5.62 1.41 2 0.70 ICP-MS -1.46 -2.83 a
N11 12% 8.8 0.2 8.8 0.2 2 0.1 ICP 0.55 2.05 b
N12 12% 7.298 0.726 7.298 0.726 2 0.363 HG-AAS -0.40 -1.16 b
N13 12% 6.8 0.38 6.8 0.38 2 0.19 ICP-MS -0.71 -2.50 b
N14 DM 5.3584 1.0181 4.7154 0.8959 2 0.4480 ICP-IDMS -2.03 -5.29 a
N15 12% 5.5 0.77 5.5 0.77 2 0.39 GF-AAS -1.53 -4.32 b
N16 12% 5.44 0.98 5.44 0.98 2 0.49 ICP-MS -1.57 -3.90 a
N17 DM 12 4 10.56 3.52 2 1.76 ICP-OES 1.66 1.45 c
N18 DM 8.36 2.431 7.36 2.14 2 1.07 ICP -0.36 -0.50 a
N19 12% 9.115 2.538 9.115 2.538 2 1.27 HG-AAS 0.75 0.89 a
N20 DM 4 2.31 3.52 2.03 2 1.02 HG-AAS -2.78 -4.02 a
N22 DM 6.89 1.43 6.06 1.26 2 0.63 ICP-MS -1.18 -2.49 a
N23 NC 8.5 7.48 HG-AAS -0.29 -1.10 b
N26 DM 8.9 1.5 7.83 1.32 2 0.66 ICP-MS -0.06 -0.13 a
N27 12% 8.9 1.1 8.9 1.1 2 0.55 Z-ET-AAS 0.61 1.41 a
N28 DM 4.9 1.1 4.31 0.97 2 0.48 SFICP-MS -2.28 -5.70 a
N29 NC 5.7 0.34 5.02 0.30 2 0.15 ICP -1.84 -6.67 b
N30 DM 7.2 1.5 6.34 1.32 2 0.66 ICP-MS -1.01 -2.05 a
N31 DM 8.69 1.304 7.65 1.15 2 0.57 GF-AAS -0.18 -0.40 a
N33 DM 4.16 0.97 3.66 0.85 2 0.43 SFICP-MS -2.69 -7.21 a
N35 DM 9.71 0.68 8.54 0.60 2 0.30 k0-INAA 0.39 1.20 b
N37 DM 6.17 0.62 5.43 0.55 2 0.27 ICP-MS -1.58 -5.07 b
N38 DM 5.65 0.56 4.97 0.49 3.18 0.15 ICP -1.87 -6.74 b
N41 NC 6.554 1.311 5.77 1.15 2 0.58 HG-AAS -1.36 -3.06 a
L24 NC 9.23 0.7 8.12 0.62 2 0.308 ET-AAS 0.12 0.37 b
L39 DM 5.59 0.44 4.92 0.39 4.3 0.01 HG-AAS -1.90 -7.33 b
L42 12% 4.92 1.41 4.92 1.41 2 0.71 ICP-MS -1.90 -3.69 a
L43 DM 5.17 4.55 ICP-MS -2.13 -8.23 b
L44 DM 6.8 1.5 5.98 1.32 2 0.66 ICP -1.23 -2.51 a
L45 DM 4.56 0.4 4.01 0.35 2 0.176 HG-AAS -2.47 -8.76 b
EURL-HM-21: Total As in kaolinitic clay
Xref = 7.93; Uref (k=2) = 0.82; σ = 1.59 (all values in mg kg-1, referring to 12% moisture content)
Measurement results and associated expanded measurement uncertainties (referring to 12% moisture content)
N20
N33
L45
N28
L43
N01
N14
L39
L42
N38
N29
N07
N09
N37
N16
N15
N10
N41
N02
N04
L44
N22
N30
N03
N08
N13
N12
N18
N23
N31
N06
N26
L24
N35
N11
N27
N19
N17
0
2
4
6
8
10
12
14
NRLs
OCLs
Xref
Xref
± Uref
Xref
± 2
ma
ss fra
ctio
n (
mg
kg
-1)
Laboratory code
Xref
Annex 9: Results for inorganic arsenic (iAs)
DM: dry mass; NC: not corrected for moisture content; 12 %: moisture content of 12 %.
33
EURL-HM-21: iAs in kaolinitic clay
Measurement results and associated expanded measurement uncertainties
(referring to 12% moisture content)
N10
N38
N12
N13
N07
N11
N04
L25
N01
N20
L45
N26
L44
0
2
4
6
8
NRLs
OCLs
ma
ss fra
ctio
n (
mg
kg
-1)
Laboratory code
Xref
(tot As)
Annex 10: Results for total cadmium (Cd)
Consensus from participants:
Xcons = 0.065 mg kg-1, referring to 12% moisture content
DM: dry mass; NC: not corrected for moisture content; 12 %: moisture content of 12 %.
Lab
codeXlab Ulab Xlab12% Ulab12% k ulab12% Technique
N01 12% 0.0611 0.0305 0.0611 0.0305 2 0.0153 ICP-MS
N02 NC 0.067 0.0098 0.059 0.009 2 0.004 AAS
N03 DM 0.086 0.008 0.076 0.007 2 0.004 ICP
N04 DM 0.064 0.03 0.056 0.026 2 0.013 ICP-MS
N05 DM < 0.5 AAS
N06 DM < 0.2 ICP
N07 12% 0.053 0.011 0.053 0.011 2 0.006 ICP-MS
N08 12% 0.098 0.027 0.098 0.027 2 0.014 ICP-MS
N09 DM 0.0593 0.0071 0.0522 0.0062 2 0.0031 ICP-MS
N10 DM 0.046 0.015 0.040 0.013 2 0.007 ICP-MS
N11 12% 0.052 0.01 0.052 0.01 2 0.005 ICP
N12 12% 0.065 0.017 0.065 0.017 2 0.009 ET-AAS
N13 12% 0.063 0.0044 0.063 0.0044 2 0.0022 ICP-MS
N14 DM 0.0495 0.0094 0.0436 0.0083 2 0.0041 ICP-IDMS
N15 12% 0.054 0.007 0.054 0.007 2 0.004 GF-AAS
N16 12% 0.065 0.013 0.065 0.013 2 0.007 ICP-MS
N17 DM < 0.1 ICP-OES
N18 DM 0.089 0.016 0.078 0.014 2 0.007 AAS
N19 12% 0.0616 0.0157 0.0616 0.0157 2 0.008 GF-AAS
N20 DM 0.05 0.011 0.044 0.010 2 0.005 ET-AAS
N22 DM 0.06 0.01 0.053 0.009 2 0.004 ICP-MS
N23 NC 0.074 0.065 GF-AAS
N26 DM 0.086 0.015 0.076 0.013 2 0.007 ICP-MS
N27 12% < 0.25 Z-ET-AAS
N28 DM 0.049 0.021 0.043 0.018 2 0.009 ET-AAS
N29 NC 0.07 0.02 0.062 0.018 2 0.009 ICP
N30 DM 0.556 0.093 0.489 0.082 2 0.041 ICP-MS
N31 DM 0.113 0.017 0.099 0.015 2 0.007 GF-AAS
N32 DM 0.078 0.014 0.069 0.012 2 0.006 AAS
N33 DM 0.0742 0.0147 0.065 0.013 2 0.006 SFICP-MS
N37 DM 0.061 0.006 0.054 0.005 2 0.003 ICP-MS
N38 DM 0.06 0.006 0.053 0.005 3.18 0.002 ICP
N41 NC 0.063 0.017 0.055 0.015 2 0.007 GF-AAS
L24 NC 0.069 0.011 0.061 0.010 2 0.005 ET-AAS
L36 DM 0.48 0.04 0.422 0.035 2 0.018 AAS
L39 DM < 0.100 AAS
L43 DM 0.088 0.077 ICP-MS
L42 12% 0.07 0.009 0.07 0.009 2 0.005 ICP
L44 DM 0.4 0.272 0.352 0.239 2 0.120 ICP
L45 DM 0.13 0.03 0.114 0.026 2 0.013 AAS
EURL-HM-21: Total Cd in kaolinitic clay
Xcons = 0.065 mg kg-1, referring to 12% moisture content
Measurement results and associated expanded measurement uncertainties (referring to 12% moisture content)
N10
N28
N14
N20
N11
N09
N22
N38
N07
N37
N15
N41
N04
N02
L24
N01
N19
N29
N13
N12
N16
N23
N33
N32
L42
N03
N26
L43
N18
N08
N31
L45
L44
L36
N30 --
0.0
0.1
0.2
0.3
0.4
0.5
0.6
NRLs
OCLs
Xcons
ma
ss fra
ctio
n (
mg
kg
-1)
Laboratory code
Xcons
Annex 11: Results for total mercury (Hg)
Assigned values: Xref = 0.047; Uref (k=2) = 0.004; σ = 0.012
(all values in mg kg-1, referring to 12% moisture content)
a performance: satisfactory, questionable, unsatisfactory, b a: uref ≤ ulab ≤ σ; b: ulab < uref; and c: ulab > σ
DM: dry mass; NC: not corrected for moisture content; 12 %: moisture content of 12 %.
Lab
codeXlab Ulab Xlab12% Ulab12% k ulab12% Technique z-score
aζ-score
aMU
b
N01 12% 0.0454 0.0227 0.0454 0.0227 2 0.011 ICP-MS -0.11 -0.11 a
N02 NC 0.21 0.048 0.18 0.042 2 0.021 CV-AAS 11.85 6.50 c
N03 DM < 0.05 ICP
N04 DM 0.03 0.012 0.026 0.011 2 0.005 ICP-MS -1.74 -3.48 a
N05 DM 0.0487 0.0019 0.0429 0.002 2 0.001 DMA -0.32 -1.46 b
N06 DM < 0.05 DMA
N07 12% 0.044 0.007 0.044 0.007 2 0.004 DMA -0.23 -0.62 a
N08 12% 0.045 0.009 0.045 0.009 2 0.005 DMA -0.14 -0.32 a
N09 DM 0.0469 0.0047 0.0413 0.004 2 0.002 DMA -0.46 -1.67 b
N10 DM 0.061 0.018 0.054 0.016 2 0.008 DMA 0.60 0.85 a
N11 DM 0.053 0.01 0.047 0.009 2 0.004 ICP 0.00 0.00 a
N12 12% 0.047 0.008 0.047 0.008 2 0.004 CV-AFS 0.03 0.08 a
N13 12% 0.054 0.0057 0.054 0.0057 2 0.003 ICP-MS 0.63 1.96 a
N14 DM 0.0413 0.0022 0.0363 0.002 2 0.001 DMA -0.88 -3.90 b
N15 12% 0.051 0.009 0.051 0.009 2 0.005 CV-AAS 0.37 0.85 a
N16 12% 0.058 0.009 0.058 0.009 2 0.005 ICP-MS 0.97 2.22 a
N17 DM 0.042 0.003 0.037 0.003 2 0.001 DMA -0.83 -3.47 b
N18 DM 0.071 0.013 0.062 0.011 2 0.006 DMA 1.36 2.54 a
N19 12% 0.057 0.0065 0.057 0.0065 2 0.003 CV-AAS 0.89 2.54 a
N20 DM 0.1 0.03 0.09 0.026 2 0.013 CV-AAS 3.55 3.08 c
N22 DM < 0.05 ICP-MS
N26 DM 0.069 0.011 0.061 0.010 2 0.005 ICP-MS 1.21 2.59 a
N27 12% 0.047 0.008 0.047 0.008 2 0.004 DMA 0.03 0.08 a
N28 DM 0.078 0.034 0.069 0.030 2 0.015 CV-AAS 1.89 1.45 c
N29 NC < 0.08 ICP
N30 DM 0.038 0.012 0.0334 0.011 2 0.005 ICP-MS -1.13 -2.27 a
N31 DM 0.048 0.011 0.0422 0.010 2 0.005 DMA -0.38 -0.81 a
N32 DM < 0.1 CV-AAS
N33 DM 0.0501 0.0157 0.0441 0.014 2 0.007 SFICP-MS -0.22 -0.35 a
N35 DM 0.051 0.003 0.045 0.003 2 0.001 CV-AAS -0.15 -0.63 b
N37 DM 0.052 0.008 0.046 0.007 2 0.004 DMA -0.08 -0.21 a
N38 DM 0.045 0.015 0.040 0.013 3.18 0.004 ICP -0.60 -1.46 a
N41 NC 0.073 0.023 0.064 0.020 2 0.010 CV-AAS 1.51 1.69 a
L39 DM 0.039 0.012 0.034 0.011 2 0.005 CV-AAS -1.06 -2.12 a
L43 DM 0.057 0.050 ICP-MS 0.30 1.43 b
L44 DM < 0.025 LECO AMA
L45 DM 0.07 0.05 0.06 0.04 2 0.02 CV-AAS 1.28 0.68 c
EURL-HM-21: Total Hg in kaolinitic clay
Xref = 0.047; Uref (k=2) = 0.004; σ = 0.012 (all values in mg kg-1, referring to 12% moisture content)
Measurement results and associated expanded measurement uncertainties (referring to 12% moisture content)
N04
N30
L39
N14
N17
N38
N09
N31
N05
N07
N33
N35
N08
N01
N37
N11
N12
N27
L43
N15
N10
N13
N19
N16
N26
L45
N18
N41
N28
N20
N02
0.00
0.05
0.10
0.15
0.20
0.25
NRLs
OCLs
Xref
Xref
± Uref
Xref
± 2
ma
ss fra
ctio
n (
mg
kg
-1)
Laboratory code
Xref
Annex 12: Results for extractable lead (ex-Pb)
Assigned values: Xref = 3.15; Uref (k=2) = 0.45; σ = 0.79
(all values in mg kg-1, referring to 12% moisture content)
a performance: satisfactory, questionable, unsatisfactory, b a: uref ≤ ulab ≤ σ; b: ulab < uref; and c: ulab > σ
DM: dry mass; NC: not corrected for moisture content; 12 %: moisture content of 12 %.
Lab
codeXlab Ulab Xlab12% Ulab12% k ulab12% Technique z-score
aζ-score
aMU
b
N01 12% 2.73 1.37 2.73 1.37 2 0.69 ICP-MS -0.54 -0.59 a
N02 NC 4.35 0.59 3.83 0.52 2 0.260 AAS 0.85 1.96 a
N03 DM 75.1 7.5 66.09 6.6 2 3.3 ICP 79.79 19.03 c
N04 DM 69 34.5 60.7 30.4 2 15.18 ICP-MS 72.99 3.79 c
N05 DM 4.085 0.817 3.595 0.719 2 0.359 AAS 0.56 1.04 a
N06 DM 5.3 1.7 4.664 1.496 2 0.748 ICP 1.91 1.93 a
N07 12% 5.3 1.3 5.3 1.3 2 0.65 ICP-MS 2.72 3.12 a
N08 12% 4.6 0.78 4.6 0.78 2 0.39 ICP-MS 1.83 3.21 a
N09 DM 5.02 0.55 4.42 0.48 2 0.24 ICP-MS 1.60 3.83 a
N10 DM 4.31 1.07 3.79 0.94 2 0.47 ICP-MS 0.81 1.22 a
N11 12% 7.2 1.6 7.2 1.6 2 0.8 ET-AAS 5.13 4.87 c
N12 12% 4.5 0.67 4.5 0.67 2 0.34 ICP-MS Q 1.71 3.34 a
N13 12% 3.7 0.35 3.7 0.35 2 0.18 ICP-MS 0.69 1.92 b
N15 12% 4.8 0.5 4.8 0.5 2 0.25 GF-AAS 2.09 4.90 a
N17 DM 79 20 69.5 17.6 2 8.8 ICP-OES 84.15 7.54 c
N18 DM 4.106 1.198 3.613 1.054 2 0.527 AAS 0.58 0.80 a
N19 12% 4.079 0.9635 4.079 0.9635 2 0.482 GF-AAS 1.17 1.74 a
N20 DM 4 0.89 3.5 0.78 2 0.4 ET-AAS 0.46 0.81 a
N22 DM 10.09 3.25 8.88 2.86 2 1.43 ICP-MS 7.26 3.95 c
N23 NC 80.3 70.7 ICP 85.60 300.85 b
N26 DM 3.8 0.5 3.34 0.4 2 0.22 ICP-MS 0.24 0.60 b
N27 12% 4.9 0.6 4.9 0.6 2 0.3 Z-ET-AAS 2.21 4.66 a
N28 DM 5.39 1.51 4.74 1.33 2 0.66 ET-AAS 2.01 2.27 a
N29 NC 60.5 15.3 53.2 13.5 2 6.73 ICP 63.50 7.44 c
N30 DM 3.63 0.62 3.19 0.55 2 0.27 ICP-MS 0.05 0.11 a
N31 DM 3.389 0.508 2.982 0.447 2 0.224 GF-AAS -0.22 -0.54 b
N32 DM 3.96 0.713 3.48 0.63 2 0.31 AAS 0.42 0.86 a
N37 DM 3.57 0.36 3.14 0.32 2 0.1584 ICP-MS -0.02 -0.05 b
N38 DM 3.98 0.7 3.50 0.62 3.2 0.19 ICP 0.44 1.17 b
N41 NC 6.683 1.337 5.88 1.18 2 0.59 GF-AAS 3.46 4.33 a
L36 DM 3.4 0.39 2.99 0.34 2 0.195 AAS -0.21 -0.55 b
L39 DM 3.98 0.74 3.50 0.65 3.18 0.23 AAS 0.44 1.08 a
L42 12% 46.5 11.7 46.5 11.7 2 5.85 ICP-MS 54.96 7.40 c
L43 DM 74.3 65.4 ICP-MS 78.90 277 b
L44 DM 13.1 4.4 11.5 3.9 2 2.2 ICP 10.62 3.79 b
L45 DM 73.8 15.6 64.9 13.7 2 7.8 AAS 78.34 7.92 c
EURL-HM-21: ex-Pb in kaolinitic clay
Xref = 3.15; Uref (k=2) = 0.45; σ = 0.79 (all values in mg kg-1, referring to 12% moisture content)
Measurement results and associated expanded measurement uncertainties (referring to 12% moisture content)
N01
N31
L36
N37
N30
N26
N32
L39
N38
N20
N05
N18
N13
N10
N02
N19
N09
N12
N08
N06
N28
N15
N27
N07
N41
N11
N22
L44
L42
N29
N04
L45
L43
N03
N17
N23
0
3
6
9
12
15
40
60
80
100
NRLs
OCLs
Xref
Xref
± Uref
Xref
± 2
ma
ss fra
ctio
n (
mg
kg
-1)
Laboratory code
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0 2 4 6 8 10 12 14
Kernel Density Plotextractable Lead
CMW CWM
Xref
40
Annex 13: Experimental details and scoring (z-scores)
R Spiking CRM Weighed
mass (g)
Volume HNO3
(mL)
Extraction
time (min.)
External
Cal.?
Standard
additions?
As CMW HNO3 No No 100 0.025
Cd CMW HNO3 No No 100 0.006
Hg CMW HNO3 No No 100 0.013
iAs Other HNO3 No No 100 0.02
Ex-Pb Other No No 100 0.04 1 8 ml 30 Yes No
As CMW H2O2+HNO3 No No 80-110 No Yes 0.067
Cd CMW H2O2+HNO3 No No 80-110 No Yes 0.0033
Hg CMW H2O2+HNO3 No No 80-110 No Yes 0.050
Ex-Pb Other No No No No 2 85 ml 30 Yes No
As CMW H2O2+HCl+HNO3 No No 80-110 Yes 0.005
Cd CMW H2O2+HCl+HNO3 No No Yes 0.005
Hg CMW H2O2+HCl+HNO3 No No Yes 0.05
Ex-Pb CMW No No Yes 0.010 0.5 10 30 Yes
As CMW HNO3 Yes
Cd CMW HNO3 Yes
Hg CMW HNO3 Yes
iAs CMW HCl Yes
Ex-Pb CMW Yes
Cd DA HNO3No No 0.163
Hg No No 0.0005
Ex-Pb No No 2 85 mL 30 No No
As CMW H2O2+HNO3Yes No 95 No Yes 2
Cd CMW H2O2+HNO3Yes No 92 No Yes 0.1
Hg Other Yes No 96 No Yes 0.050
iAs CMW HCl Yes No 93 No Yes 0.050
Ex-Pb Other Yes No No No 1.0 0.25-0.50 50 ml 30 Yes No
As CMW HNO3No No 100 No Yes 0.0012
Cd CMW HNO3No No 100 No Yes 0.0003
Hg No No 100 No Yes 0.000051
iAs CMW H2O2+HNO3No No 100 No Yes 0.0024
Ex-Pb Other No No No 0.0018 1 8 30 Yes No
As CMW H2O2+HNO3No No 95 Yes No
Cd CMW H2O2+HNO3No No 105 Yes No
Hg Other No No 97 Yes No
Ex-Pb Other No No 97 Yes No 0.5 50 mL 30 Yes No
As CMW H2O2+HNO3Yes No 100 No Yes 0.001
Cd CMW H2O2+HNO3Yes No 104 No Yes 0.0003
Hg Other Yes No 99 No Yes 0.0001
Ex-Pb Other Yes No 102 No Yes 0.018 0.2 50 30 Yes No
Recovery (R, in %)Experimental details for Ex-Pb
For the determination of As (m/z 75) with ICPMS there is
an interference on Sm or Nd (m/z 150++), so we
measured As in MS/MS mode with O2 (m/z 91)
We also analyzed extractable As, together with
extractable Pb, applying the method prescribed in the
legislation for extractable Pb. The result for extractable
As was 1.2 mg/Kg.
N01
N02
N08
N06
N07
N04
N05
N09
N03
Lab IDSample
digestionDigestion mixture
Std.
method?
Correct
recovery?
LOD
(mg/Kg)Additional remarks regarding the method of analysis?
41
Estimation Reported
As Yes 250-1000 Yes Yes Yes Yes
Cd Yes > 1000 Yes Yes Yes Yes
Hg Yes > 1000 Yes Yes Yes Yes
iAs Yes 50-250 Yes Yes Yes
Ex-Pb Yes 0-50 Yes Yes Yes Yes
As No 50-250 Yes Yes Yes Yes
Cd No 50-250 Yes Yes Yes Yes
Hg No Never Yes Yes Yes
Ex-Pb No Never Yes Yes Yes
As No 0-50 Yes Yes Yes
Cd No 0-50 Yes Yes Yes
Hg No 0-50 Yes Yes Yes
Ex-Pb No 0-50 Yes Yes Yes
As No > 1000 No Yes Yes
Cd No > 1000 No Yes Yes
Hg No > 1000 No Yes Yes
iAs No 250-1000 No Yes
Ex-Pb No > 1000 No Yes Yes
Cd Yes Yes 50-250 No Yes Yes Yes
Hg Yes Yes 50-250 No Yes Yes Yes
Ex-Pb Yes Yes No Yes Yes
As No 0-50 Yes Yes No
Cd No 0-50 Yes Yes No
Hg No 0-50 Yes Yes No
iAs No 0-50 Yes Yes No
Ex-Pb No 0-50 Yes Yes No
As Yes Yes 0-50 No Yes Yes
Cd Yes Yes 0-50 No Yes Yes
Hg Yes Yes 0-50 No Yes Yes
iAs Yes Yes 0-50 No Yes Yes
Ex-Pb Yes Yes Never No Yes Yes
As Yes Yes 50-250 Yes Yes Yes Yes
Cd Yes Yes 50-250 Yes Yes Yes Yes
Hg Yes Yes 50-250 Yes Yes Yes Yes
Ex-Pb Yes Yes Never Yes Yes Yes
As Yes Yes 50-250 Yes Yes Yes Yes
Cd Yes Yes 50-250 Yes Yes Yes Yes
Hg Yes Yes 50-250 Yes Yes Yes Yes
Ex-Pb Yes Yes 0-50 Yes Yes Yes Yes
Quality
system
From in-house validation, Estimation
based on judgment
From in-house validation
Uncertainty budget (ISO GUM), From
in-house validation
N04
N05
N06
N07
N08
ILC? Do you have any comments? Let us know!
Measurement Uncertainty
From interlaboratory comparison data
From in-house validation
From in-house validation
Accredited?CRM for
Ins. cal.?
Moisture
correction?Moisture (% m/m)
Samples /
yearLab ID
N01
N02
N03 Uncertainty budget (ISO GUM)
From in-house validation
N09
0,86
0.77
0.69 % (The results
are refer to a 12 % of
water content)
1.2 %; afterwards
result corrected to 12
% moisture content
0.407
According to the report of the workshop 2014 the results are reported relative to a feedingstuff with a
moisture content of 12 %
Measurements results can affect: unusual matrix, we doesn’t have the same reference material and No
specific sample preparation method for kaolinitic clay. For ext. Pb determination we used the same
method as for As and Cd (microwave digestion)
We used the routine analyse for Pb
We have analyzed inorganic As in the sample by HPLC-ICP-MS, applying the same extraction method we
use for food matrixes (microwave -50 min in HNO3 0.3% + 3%H2O2). However, the result was very low
compare to total As, so we think that the extraction conditions are too soft to recover the As in this kind of
matrix.
Our reported results in table are recalculated as concentration of HM in 100%of dry mass. Our NRL used
to express results for feed refer to a moisture content of 12% in accordance with Directive 2002/32/EC.
42
R Spiking CRM Weighed
mass (g)
Volume HNO3
(mL)
Extraction
time (min.)
External
Cal.?
Standard
additions?
As CMW HNO3 No No 100 Yes 0.05
Cd CMW HNO3 No No 100 Yes 0.01
Hg Other No No 100 Yes 0.01
iAs Other No No 100 Yes 0.100
Ex-Pb Other No No 100 Yes 0.01 1 20 30 No No
As CMW HNO3 No No
Cd CMW HNO3 No No
Hg CMW HNO3 No No
iAs Other No No
Ex-Pb Other No No 2 86 30 Yes No
As CMW HNO3+HF No Yes 94 Yes Yes 0.075
Cd CMW HNO3+HF No Yes 106 Yes Yes 0.0024
Hg CMW HNO3+HF No Yes 120 Yes Yes 0.010
iAs CMW H2O2+HNO3No Yes 30 Yes 0.010
Ex-Pb CMW No Yes 98 Yes Yes 0.002 0.5 21 mL 30 Yes Yes
As CMW HNO3 No Yes 100 Yes Yes 0,0025
Cd CMW HNO3 No Yes 105 Yes Yes 0,0007
Hg CMW HNO3 No Yes 94 Yes Yes 0,0005
iAs Other H2O2+HNO3No Yes 100 Yes Yes 0,030
Ex-Pb Other No Yes 99 Yes Yes 2 100 ml 30 Yes No
As CMW H2O2+HNO3 Yes No
Cd CMW H2O2+HNO3Yes No
Hg CMW H2O2+HNO3 Yes No
As CMW H2O2+HNO3 No No 92.8 Yes 0.050
Cd CMW H2O2+HNO3No No 101.2 Yes 0.050
Hg CMW H2O2+HNO3No No 95.5 Yes 0.02
Ex-Pb Other No No 102.6 Yes 0.50 0.20 100 30 Yes No
As CMW H2O2+HNO3 No No
Cd CMW H2O2+HNO3No No
Hg CMW H2O2+HNO3 No No
As CMW H2O2+HNO3 No Yes 99,7 Yes Yes 0,5
Cd CMW H2O2+HNO3No Yes 97,0 Yes Yes 0,1
Hg No Yes Yes 0,01
Ex-Pb CMW No Yes 82,9 Yes Yes 0,5 0,55 5ml Yes No
As CMW HCl+HNO3 No No 121 No Yes 0.001
Cd CMW HCl+HNO3 No No 114 No Yes 0.001
Hg CMW HCl+HNO3 No No 114 No Yes 0.001
Ex-Pb Other No No 92 No Yes 0.002 0.500 10 ml 30 Yes No
As DA HCl+HNO3Yes No 96.84 No Yes 0.1
Cd CMW H2O2+HNO3 Yes No 96.97 No Yes 0.003
Hg CMW H2O2+HNO3 Yes No 88.64 No Yes 0.003
Ex-Pb Other Yes No 81.32 No Yes 0.050 2 85 30 Yes No
The sample for As, Cd and Pb analysis was digested
under pressure: 0,55 g / 5 ml 67 % HNO3 /in 50 ml
For all analitical method used, at the bottom of all
crucibles and digestion vessels, there was a white
sediment.
N17
N18
N19
N16
N13
N14
Lab ID
N10
N12
N11
N15
Sample
digestion
Results reported as 12 % moisture
Digestion mixtureStd.
method?
Correct
recovery?
Recovery (R, in %)
LOD
(mg/Kg)Additional remarks regarding the method of analysis?
Experimental details for Ex-Pb
43
Estimation Reported
As Yes Yes 50-250 Yes Yes Yes
Cd Yes Yes 50-250 Yes Yes Yes
Hg Yes Yes 50-250 Yes Yes Yes
iAs Yes Yes 0-50 Yes Yes Yes
Ex-Pb Yes Yes 0-50 Yes Yes Yes
As Yes 50-250 Yes Yes No Yes
Cd Yes 50-250 Yes Yes No Yes
Hg Yes 50-250 Yes Yes No Yes
iAs Yes 0-50 Yes Yes No
Ex-Pb Yes Yes Yes No
As Yes 0-50 Yes Yes Yes Yes
Cd Yes 0-50 Yes Yes Yes Yes
Hg Yes 0-50 Yes Yes Yes Yes
iAs Yes 0-50 Yes Yes Yes
Ex-Pb Yes 0-50 Yes Yes Yes
As Yes 250-1000 Yes Yes Yes Yes
Cd Yes 250-1000 Yes Yes Yes Yes
Hg Yes 250-1000 Yes Yes Yes Yes
iAs Yes 0-50 Yes Yes Yes Yes
Ex-Pb Yes Never Yes Yes Yes
As Yes Yes 250-1000 Yes Yes Yes
Cd Yes Yes 250-1000 Yes Yes Yes
Hg Yes Yes 250-1000 Yes Yes Yes
As Yes Yes 0-50 Yes Yes No Yes
Cd Yes Yes 0-50 Yes Yes No Yes
Hg Yes Yes 0-50 Yes Yes No Yes
Ex-Pb Yes Yes 0-50 Yes Yes No
As Yes No 0-50 Yes Yes No
Cd Yes No 0-50 Yes Yes No
Hg Yes No 0-50 Yes Yes No
As Yes 50-250 Yes Yes Yes Yes
Cd Yes 50-250 Yes Yes Yes Yes
Hg Yes 50-250 Yes Yes Yes Yes
Ex-Pb Yes Yes Yes Yes
As Yes Yes 0-50 Yes Yes Yes Yes
Cd Yes Yes 0-50 Yes Yes Yes Yes
Hg Yes Yes 0-50 Yes Yes Yes Yes
Ex-Pb Yes Yes Never Yes Yes Yes
As No 250-1000 No Yes Yes Yes
Cd No 250-1000 No Yes Yes Yes
Hg No 250-1000 No Yes Yes Yes
Ex-Pb No No Yes Yes
All results are in mg/ kg (ppm) relative to a feedingstuff with a moisture content of 12 %
For Cd determination, we also used the extractable Cd method and results was comparable with those
obtained by digestion method.
Samples /
year
Measurement Uncertainty
Quality
system
0.38
0.6
0.5
0.44
0,81
it was written
"Concentration in dry
mass" on the result
input page (moisture
content : 0.5 %)
Moisture (% m/m)
0,3
0.86
N14
N15
N16
N17
N13
Lab ID
N11
N12
CRM for
Ins. cal.?
From in-house validation, From
interlaboratory comparison data
Uncertainty budget (ISO GUM), From
in-house validation
Uncertainty budget (ISO GUM), From
in-house validation
From in-house validation, From
interlaboratory comparison data
From interlaboratory comparison data
From in-house validation
From in-house validation
From in-house validation
From in-house validation
From in-house validation
ILC? Do you have any comments? Let us know!Accredited?Moisture
correction?
N18
N19
N10
44
R Spiking CRM Weighed
mass (g)
Volume HNO3
(mL)
Extraction
time (min.)
External
Cal.?
Standard
additions?
As DA HCl+HNO3Yes Yes 108 Yes No 0.125
Cd CMW HNO3Yes Yes 115 Yes No 0.003
Hg CMW HNO3Yes Yes 99 Yes No 0.025
iAs DA HCl+HNO3Yes Yes 54 Yes No 0.125
Ex-Pb Other Yes Yes 139 Yes No 0.25 0.2 85mL 30 Yes No
As CMW H2O2+HNO3 No Yes 109.8 Yes 0.05
Cd CMW H2O2+HNO3 No Yes 115.4 Yes 0.003
Hg CMW H2O2+HNO3 No Yes 118.4 Yes 0.01
Ex-Pb Other No Yes 0.03 0.50 10 30 No No
As CMW H2O2+HNO3 No 91 No Yes
Cd CMW H2O2+HNO3 No 91 No Yes
Ex-Pb CMW No 0.5 8 mL No No
As CMW HCl+HNO3+HF No
Cd CMW HCl+HNO3+HF No
L25 iAs Other No Yes 121 Yes 0.01
As CMW HCl+HNO3No Yes 98 Yes Yes 0.01
Cd CMW HCl+HNO3No Yes 98 Yes Yes 0.001
Hg CMW HCl+HNO3No Yes 97 Yes Yes 0.02
iAs Other HCl No Yes 73 Yes Yes 0.05
Ex-Pb Other No Yes 102 Yes No 0.01 2 85 30 Yes No
As CMW H2O2+HNO3+HF Yes Yes 104.5 No Yes 0.18
Cd CMW H2O2+HNO3+HF Yes Yes 108.5 No Yes 0.075
Hg Yes Yes 99.8 No Yes 0.010
Ex-Pb Other Yes Yes 101.1 No Yes 2 85 30 Yes No
As CMW H2O2+HNO3 Yes No No 0,2
Cd CMW H2O2+HNO3 Yes No No
Hg CMW H2O2+HNO3 Yes No No 0.02
Ex-Pb Other Yes No No 0.012 2 30 Yes
As CMW H2O2+HNO3 No Yes 98 Yes
Cd CMW H2O2+HNO3 No Yes 101 Yes
Hg CMW H2O2+HNO3 No Yes 98 Yes
Ex-Pb CMW No Yes 101 Yes 0.5 3 20 Yes No
As CMW H2O2+HNO3 No Yes 100 No Yes 0.008
Cd CMW H2O2+HNO3 No Yes 89 No Yes 0.002
Hg CMW H2O2+HNO3 No Yes 84 No Yes 0.007
Ex-Pb Other No Yes 100 No Yes 0.005 2 85 mL 30 Yes No
As CMW HNO3+HF No No No No 0,01
Cd CMW HNO3+HF No No No No 0,01
Hg Other No No No No 0,001
Ex-Pb Other No No No No 0,01 0.5 30 30 Yes No
N26
Correct
recovery?
Recovery (R, in %)
LOD
(mg/Kg)Additional remarks regarding the method of analysis?
Experimental details for Ex-Pb
Did Not recovery correct for Extractable Pb ( No CRM
available)
N20
L24
N27
N22
N23
Lab IDSample
digestionDigestion mixture
Std.
method?
N28
N30
N31
N29
45
Estimation Reported
As Yes 0-50 No Yes Yes
Cd Yes 250-1000 No Yes Yes
Hg Yes 0-50 No Yes Yes
iAs Yes 0-50 No Yes Yes
Ex-Pb Yes 0-50 No Yes Yes
As Yes > 1000 No Yes Yes
Cd Yes > 1000 No Yes Yes
Hg Yes > 1000 No Yes Yes
Ex-Pb Yes 0-50 No Yes Yes
As No No 0-50 Yes
Cd No No 0-50 Yes
Ex-Pb No No Never Yes
As No Yes
Cd No Yes
L25 iAs Yes Yes 0.4 Never From in-house validation No Yes No Sample quantity was very small.
As Yes > 1000 No Yes No Yes
Cd Yes > 1000 No Yes No Yes
Hg Yes > 1000 No Yes No Yes
iAs Yes 50-250 No Yes No Yes
Ex-Pb Yes Never No Yes No
As Yes 250-1000 Yes Yes Yes Yes
Cd Yes 250-1000 Yes Yes Yes Yes
Hg Yes 250-1000 Yes Yes Yes Yes
Ex-Pb Yes Yes Yes Yes
As Yes 50-250 Yes Yes No
Cd Yes 50-250 Yes Yes No Yes
Hg Yes 50-250 Yes Yes No Yes
Ex-Pb Yes Never Yes Yes No Yes
As No 250-1000 Yes Yes Yes Yes
Cd No 250-1000 Yes Yes Yes Yes
Hg No 50-250 Yes Yes Yes Yes
Ex-Pb No 250-1000 Yes Yes Yes Yes
As Yes 0-50 No Yes No
Cd Yes 0-50 No Yes No
Hg Yes 0-50 No Yes No
Ex-Pb Yes 0-50 No Yes No
As Yes No Never No Yes No
Cd Yes No Never No Yes No
Hg Yes No Never No Yes No
Ex-Pb No Never No Yes No
N26 0.9 From interlaboratory comparison data
Samples /
year
Measurement Uncertainty
Quality
system
This laboratory does Not analyses Feed samples and does Not have accreditation for heavy metals in
Feed. It is accredited for Heavy Metals in all Food matrices
Do you have any comments? Let us know!
To low amount of sample for PT
Result of 12% of moisture. Results of Pb in ZETAAAS after microwave digestion in very different
ILC? Accredited?Lab IDCRM for
Ins. cal.?
Moisture
correction?Moisture (% m/m)
1.51
0.51
0.80
N29
0.6
91
0.77
From replicates (precision), From
interlaboratory comparison data
Uncertainty budget (ISO GUM), From
in-house validation, From replicates
(precision), From interlaboratory
comparison data
From replicates (precision),
Estimation based on judgment
Uncertainty budget (ISO GUM), From
in-house validation, From replicates
(precision)
From in-house validation
From in-house validation
From interlaboratory comparison data
From in-house validation
N31
N20
N22
N23
L24
N27
N28
N30
46
R Spiking CRM Weighed
mass (g)
Volume HNO3
(mL)
Extraction
time (min.)
External
Cal.?
Standard
additions?
Cd Other No Yes 93 Yes No 0.002
Hg CMW HF No Yes 97 Yes No 0.05
Ex-Pb No Yes 80 Yes No 0.007 1 25 30 Yes Yes
As CMW H2O2+HNO3+HF Yes No Yes 0,005
Cd CMW H2O2+HNO3+HF Yes No Yes 0,001
Hg CMW H2O2+HNO3+HF Yes No Yes 0,01
As Other No No 0.31
Hg Other HCl+HNO3+HF No No 0.001
Cd Other HNO3No Yes 94.6 Yes Yes 0.30
Ex-Pb Other No Yes 104.9 Yes 1.35 2 85 mL 30
As Other HCl+HNO3No No Yes 0.006
Cd Other HCl+HNO3No No Yes 0.006
Hg DA No No Yes 0.0003
Ex-Pb Other No No Yes 0.09 2 85 30 Yes No
As CMW H2O2+HNO3 Yes No 113 Yes No 0.1
Cd CMW H2O2+HNO3 Yes No 100 Yes No 0.02
Hg CMW H2O2+HNO3 Yes No Yes No 0.025
iAs Other HCl Yes No 110 Yes No 0.1
Ex-Pb Other Yes No No No 0.02 0,5 25 ml 30 Yes No
As DA Yes No 78 Yes No 0.003
Cd DA Yes No 0.100
Hg Other HNO3+H2SO4Yes No 0.010
Ex-Pb Other Yes No 0.50 0,5 25 ml 30 Yes No
As CMW H2O2+HNO3 Yes No 96 Yes 0,05
Cd CMW H2O2+HNO3 Yes No 108 Yes 0,05
Hg CMW H2O2+HNO3 Yes No 94 Yes No 0,05
Ex-Pb CMW Yes No 98 Yes No 0,05 2,00 85ml 30 Yes Yes
As CMW H2O2+HNO3 No No 90.2 Yes 0.03
Cd CMW H2O2+HNO3 No No 95.6 Yes 0.06
Ex-Pb CMW No No 118 Yes 0.02 0.5 200 30 Yes No
As CMW HNO3No Yes 116 Yes 0.1
Cd CMW HNO3No Yes 103 Yes 0.02
Hg CMW HNO3No Yes 116 Yes 0.02
Ex-Pb CMW No Yes 98 Yes 0.1 0.5
As DA HCl No Yes 97 Yes No 0.025
Cd DA HCl No Yes 93 Yes No 0.03
Hg H2SO4 HCl+HNO3+H2SO4 No Yes 80 Yes No 0.02
iAs DA HCl No Yes 79 Yes No 0.06
Ex-Pb DA No Yes 84 Yes No 0.08 3 N/A Yes No
L43
Lab IDSample
digestionDigestion mixture
Std.
method?
Correct
recovery?
Recovery (R, in %)
LOD
(mg/Kg)Additional remarks regarding the method of analysis?
Experimental details for Ex-Pb
k0-INAA is Non-destructive technique.
L45
L42
L39
N41
The test material is Not a routine sample, the method is
Not accredited and it was first time analyzed in our lab.N32
N37
N38
N33
N35
L36
47
Estimation Reported
Cd Yes 250-1000 Yes Yes Yes
Hg Yes Never Yes Yes Yes
Ex-Pb Yes Never Yes Yes Yes
As Yes 50-250 Yes Yes Yes Yes
Cd Yes Yes 50-250 Yes Yes Yes Yes
Hg Yes Yes 50-250 Yes Yes Yes Yes
As Yes Yes 250-1000 Yes Yes Yes Yes
Hg Yes Yes 50-250 Yes Yes Yes
Cd Yes 0-50 No Yes No
Ex-Pb Yes 0-50 No Yes No
As Yes 50-250 Yes Yes Yes Yes
Cd Yes 50-250 Yes Yes Yes Yes
Hg Yes 50-250 Yes Yes Yes Yes
Ex-Pb Yes 0-50 Yes Yes Yes
As Yes No 0-50 Yes Yes No
Cd Yes No 0-50 Yes Yes No
Hg No 0-50 Yes Yes No
iAs No 0-50 Yes Yes No
Ex-Pb No 0-50 Yes Yes No
As Yes 0-50 Yes Yes No
Cd Yes 0-50 Yes Yes No
Hg Yes 0-50 Yes Yes No
Ex-Pb Yes 0-50 Yes Yes No
As No 250-1000 Yes Yes Yes Yes
Cd No 250-1000 Yes Yes Yes Yes
Hg No 50-250 Yes Yes Yes Yes
Ex-Pb No 0-50 Yes Yes Yes
As No 0-50 No Yes Yes Yes
Cd No 0-50 No Yes Yes Yes
Ex-Pb No 0-50 No Yes Yes
As Yes 250-1000 No Yes Yes
Cd Yes 250-1000 No Yes Yes
Hg Yes 250-1000 No Yes Yes
Ex-Pb Yes 250-1000 No Yes Yes
As Yes 50-250 Yes Yes Yes Yes
Cd Yes 50-250 Yes Yes Yes Yes
Hg Yes 50-250 Yes Yes Yes Yes
iAs Yes 50-250 Yes Yes Yes Yes
Ex-Pb Yes 50-250 Yes Yes Yes Yes
Quality
systemILC? Accredited? Do you have any comments? Let us know!
L43 < 0.1From in-house validation From
replicates (precision)
Lab ID
The test material is Not a routine sample, the method is Not accredited and it was first time analyzed in
our lab.
CRM for
Ins. cal.?
Moisture
correction?Moisture (% m/m)
Samples /
year
Sample size given for the PT was too small
I would like to ask you politely to send larger amount of the proficiency test item for the next time. The
amount of 15 g is really small to perform all requested measurements. Can you also mention the
information concerning determination of water content in the accompanying letter? Methods for water
content can vary through laboratories.
We have send the material to a subcontracter for analysis of total As, Cd, Hg. The aim was to check the
subcontracter
1.18
0.90
0.80
0.65
0.66
L45 1.1
L42
N41
L39
99.2N33
N35
L36
N37
N38
From in-house validation
From in-house validation
Uncertainty budget (ISO GUM), From
in-house validation, From replicates
(precision)
From replicates (precision)
Uncertainty budget (ISO GUM)
From in-house validation
Uncertainty budget (ISO GUM)
From in-house validation
Measurement Uncertainty
From replicates (precision)
Estimation based on judgment
N32
Annex 14: Compliance assessment
ML 2 or 12 mg kg-1 2 mg kg
-1 30 mg kg
-1 0.1 mg kg
-1
Lab As Cd ex-Pb Hg Compliance due to
N01 4.58 0.0611 2.73 0.0454 C
N02 5.80 0.059 3.83 0.18 C
N03 6.37 0.076 66.1 < 0.05 NC Pb
N04 5.9 0.056 60.7 0.026 NC Pb; As
N05 < 0.5 3.595 0.0429 C
N06 7.81 < 0.2 4.664 < 0.05 C
N07 5.2 0.053 5.3 0.044 NC As
N08 6.5 0.098 4.6 0.045 C
N09 5.43 0.0522 4.42 0.0413 C
N10 5.62 0.040 3.79 0.054 C
N11 8.8 0.052 7.2 0.047 NC As
N12 7.298 0.065 4.5 0.047 C
N13 6.8 0.063 3.7 0.054 C
N14 4.715 0.0436 0.0363 NC As
N15 5.5 0.054 4.8 0.051 NC As
N16 5.44 0.065 0.058 C
N17 10.6 < 0.1 69.5 0.042 C Pb
N18 7.36 0.078 3.613 0.062 C
N19 9.115 0.0616 4.079 0.057 C
N20 3.52 0.04 3.5 0.09 C
N22 6.06 0.053 8.88 < 0.05 C
N23 7.48 0.065 70.7 NC Pb
N26 7.83 0.076 3.34 0.061 C
N27 8.9 < 0.25 4.9 0.047 C
N28 4.3 0.043 4.74 0.069 NC
N29 5.0 0.062 53.2 < 0.08 C
N30 6.3 0.489 3.19 0.033 C
N31 7.65 0.099 2.982 0.042 C
N32 0.069 3.48 < 0.1 C
N33 3.66 0.0650 0.0441 NC As
N35 8.54 0.045 C
N37 5.43 0.054 3.14 0.046 C
N38 4.97 0.053 3.50 0.040 C
N41 5.770 0.055 5.88 0.064 C
L24 8.12 0.061
L36 0.42 2.99 C
L39 4.92 < 0.100 3.50 0.034 C
L42 4.92 0.07 46.5 NC Pb
L43 4.55 0.077 65.4 0.050 NC Pb; As
L44 5.98 0.35 11.50 < 0.025
L45 4.01 0.11 64.9 0.06 NC Pb
C = Compliant; NC = not-compliant; as assessed by participant
[6] and Table 2
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